Recently, various dental implants (dentistry implants) have been developed for the purpose of solving the problem of tooth loss. A general implant is provided with a fixture (also called an artificial dental root or an implant body) to be embedded into a jawbone, and an upper structure, such as an abutment, to be fixed on an upper part of the fixture. As a method to fix an abutment on a fixture, such a structure is known that an abutment is fixed on a fixture by an abutment screw (a kind of bolt).
Conventionally, technology for preventing slack of an abutment screw is disclosed, for example, by the following Patent Literature 1 to 4, however, any of them is not well-proven technology as a locking structure, and has not yet popularized.
On the other hand, the present applicant manufactures and sells Hard Lock Nut (R), which can exert a slack prevention effect higher than before, and also develops locking bolts using the principle of the Hard Lock Nut, for example, one of which is disclosed by the following Patent Literature 5.
The conventional locking bolt includes: a bolt (1) having, on its end undersurface, a truncated-conical convex portion (2) or a recess; and a disc-shaped receiver (4, 4′) having, on its upper surface, a recess (3) corresponding to the convex portion of the bolt or a convex portion corresponding to the recess thereof; wherein the receiver is formed to have an outside diameter approximately the same as an internal diameter of a screw hole (5) into which the bolt will be screwed, so that the receiver can be inserted or screwed into the screw hole (5); the recess and the convex portion, face-to-face, between the bolt and the receiver, are configured to be slightly off-centered relative to each other; and the receiver is located preliminarily at the correct position depending on the bolt size, and thus, contact between the inclined inner surface of the recess and the inclined side face of the convex portion increases a stress in a horizontal direction on the bolt and the receiver in the final screwing process of the bolt to generate a large horizontal stress therein, whereby a slack prevention effect is exerted.